The imprint of surface fluxes and transport on variations in total column carbon dioxide
- California Institute of Technology, Pasadena
- National Oceanic and Atmospheric Admin
- Jet Propulsion Laboratory, Pasadena, CA
- ORNL
- BC Consulting
- Pennsylvania State University
- University of Wisconsin, Madison
- University of Bremen, Bremen, Germany
- National Institue of Water and Atmospheric Research, New Zealand
- National Center for Atmospheric Research (NCAR)
- NASA Langley Research Center
- Harvard University
New observations of the vertically integrated CO{sub 2} mixing ratio, <CO{sub 2}>, from ground-based remote sensing show that variations in <CO{sub 2}> are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large-scale and local fluxes. Observations of both <CO{sub 2}> and CO{sub 2} concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in <CO{sub 2}> in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO{sub 2}, these synoptic-scale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in <CO{sub 2}> from covariations in <CO{sub 2}> and potential temperature, {theta}, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that simulations using Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the <CO{sub 2}> seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes and the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better fit the observations. Our simulations suggest that climatological mean CASA fluxes underestimate boreal growing season NEE (between 45-65{sup o} N) by {approx}40%. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1038495
- Journal Information:
- Biogeosciences, Vol. 9, Issue 3; ISSN 1726-4189
- Country of Publication:
- United States
- Language:
- English
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